Add shadow softness/sharpness controls in V-RayDome (with HDRI).
(Control the size of light-generating pixels within HDRI?)
In other words, if the Dome texture sampling generates internal lights, it would be nice to be able to adjust the size of the lights (soft shadows/sharp shadows).
The dome light does not generate internal lights; it works in a different way. In any case, what you want would be equivalent to essentially blurring the HDR map when it is used for illumination and/or reflections - is that what you need?